Golf club head

ABSTRACT

A golf club head according to the present invention is provided with a face portion, a crown portion, a sole portion, at least one first rib provided in the sole portion, and at least one second rib provided in the sole portion, and has an internal space surrounded by the face portion, the crown portion and the sole portion, the first rib extending in a toe-heel direction on an inner wall surface of the sole portion, the second rib extending in a face-back direction on the inner wall surface of the sole portion, and a height of the second rib from the inner wall surface of the sole portion being lower than a height of the first rib from the inner wall surface of the sole portion.

TECHNICAL FIELD

The present invention relates to a golf club head.

BACKGROUND ART

Wood-type golf club heads have undergone many refinements heretofore, and, for example, attempts have been made to improve the rebound performance, by increasing the rigidity of a sole portion. In JP 2012-396A, a rib extending in a toe-heel direction is formed on an inner surface of the sole portion, and the rigidity of the sole portion is thereby improved.

JP 2012-396A is an example of related art.

However, there is room for improving the rigidity of the sole portion, and further improvement in rigidity is desired. The present invention has been made in order to solve the above problem, and an object thereof is to provide a golf club head that is able to further improve the rigidity of the sole portion.

SUMMARY OF THE INVENTION

A golf club head according to the present invention includes a face portion, a crown portion, a sole portion, at least one first rib provided in the sole portion, and at least one second rib provided in the sole portion, the golf club head having an internal space surrounded by the face portion, the crown portion and the sole portion, the first rib extending in a toe-heel direction on an inner wall surface of the sole portion, the second rib extending in a face-back direction on the inner wall surface of the sole portion, and a height of the second rib from the inner wall surface of the sole portion being lower than a height of the first rib from the inner wall surface of the sole portion.

In the golf club head, the second rib can intersect the first rib.

In the golf club head, the first rib and the second rib can each extend continuously.

In the golf club head, a configuration can be adopted in which a thin portion having a thinnest thickness is provided in the sole portion, and the first rib and the second rib are constituted to at least partially pass through the thin portion.

In the golf club head, the thin portion can be arranged on a toe side in the toe-heel direction.

In the golf club head, a configuration can be adopted in which a thick portion having a larger thickness than the thin portion is provided in the sole portion at least partially around the thin portion, and at least one of the first rib and the second rib extends to the thick portion.

In the golf club head, a configuration can be adopted in which the golf club head includes at least two of the second rib, and the two second ribs are formed so as to intersect in the sole portion.

In the golf club head, a configuration can be adopted in which the golf club head includes one of the first rib, and an area surrounded by the one first rib and the two second ribs is arranged in the thin portion.

In the golf club head, a configuration can be adopted in which the second rib extends on a back side from a vicinity of a boundary between the face portion and the sole portion.

With the golf club head according to the present invention, the rigidity of the sole portion can be further improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a golf club head according to an embodiment.

FIG. 2 is a plan view of the golf club head of FIG. 1 in a reference state.

FIG. 3 is a plan view the golf club head in the reference state viewed from below.

FIG. 4A is a diagram illustrating a boundary of a face portion.

FIG. 4B is a diagram illustrating the boundary of the face portion.

FIG. 5 is a plan view of an inner surface viewed through a sole portion from a lower surface side.

FIG. 6 is a perspective view showing an internal space of the head with the head partially cut away.

FIG. 7 is a perspective view showing the internal space of the head viewed from a different angle to FIG. 6, with the head partially cut away.

FIG. 8 is a diagram showing an outline of the sole portion of a model of the head used in simulation.

FIG. 9A is a diagram showing a simulation result for vibration.

FIG. 9B is a diagram showing a simulation result for vibration.

FIG. 10A is a plan view showing another example of the arrangement of ribs.

FIG. 10B is a plan view showing another example of the arrangement of ribs.

FIG. 10C is a plan view showing another example of the arrangement of ribs.

FIG. 10D is a plan view showing another example of the arrangement of ribs.

FIG. 10E is a plan view showing another example of the arrangement of ribs.

EMBODIMENTS OF THE INVENTION

Hereinafter, an embodiment of a golf club head according to the present invention will be described, with reference to the drawings.

1. Overview of Golf Club Head

FIG. 1 is a perspective view of this golf club head, FIG. 2 is a plan view of the head in a reference state, and FIG. 3 is a plan view of the golf club head in the reference state viewed from below. As shown in FIGS. 1 to 3, this golf club head (hereinafter, may be referred to simply as “head”) 10 is a wood-type golf club head having a hollow structure with an internal space, and a wall surface is formed by a face portion 1, a crown portion 2, a sole portion 3 and a hosel portion 4. Specifically, the present invention can be applied to golf club heads such as utilities (hybrids), fairway woods and drivers.

The face portion 1 has a face surface that is the surface that hits the ball, and the crown portion 2 adjoins the face portion 1 and constitutes the upper surface of the head 10. The sole portion 3 mainly constitutes the bottom surface of the head 10, and constitutes the outer peripheral surface of the head 10 other than the face portion 1 and the crown portion 2. That is, in addition to the bottom surface of the head 10, the region extending from the toe side of the face portion 1 around the back side of the head to the heel side of the face portion 1 is also part of the sole portion 3. Also, as shown in FIG. 3, a fixing hole 38 for attaching a weight member (illustration omitted) is formed on the back side of the sole portion 3. A female thread (illustration omitted) for screwing in a male thread attached to the weight member is formed in the inner wall surface of the fixing hole 38.

The hosel portion 4 is a region that is provided adjoining the heel side of the crown portion 2, and has an insertion hole 41 into which a shaft (illustration omitted) of the golf club is inserted, and that is formed in a cylindrical shape extending inside the head. A center axis line Z of this insertion hole 41 coincides with the axis line of the shaft.

Here, the reference state when setting the golf club head 10 on the ground will be described. First, as shown in FIG. 2, a state where the above center axis line Z is contained in a plane P1 that is perpendicular to the ground and the head is placed on the ground at a predetermined lie angle and real loft angle is prescribed as the reference state. The plane P1 will be referred to as a reference perpendicular plane. Also, as shown in FIG. 2, the direction of the line of intersection between the reference perpendicular plane P1 and the ground will be referred to as a toe-heel direction, and the direction that is perpendicular to this toe-heel direction and parallel to the ground will be referred to as a face-back direction. Also, the direction that is orthogonal to the toe-heel direction and the face-back direction may be referred to as an up-down direction.

In the present embodiment, the boundary between the face portion 1 and the crown portion 2 and between the face portion 1 and the sole portion 3 can be defined as follows. That is, in the case where a ridgeline is formed therebetween, this ridgeline will be the boundary. On the other hand, in the case where a clear ridgeline is not formed, then in each of cross-sections E1, E2, E3 and so forth that contain a straight line N connecting a head center of gravity G and a sweet spot SS, as shown in FIG. 4A, a position Pe at which a curvature radius r of a contour line Lf of the face outer surface first reaches 200 mm in a direction toward the outer side of the face from the sweet spot side, as shown in FIG. 4B, will be the periphery of the face portion 1, and this periphery is defined as the boundary with the crown portion 2 or the sole portion 3. Note that the sweet spot SS is the point of intersection between the normal (straight line N) of the face surface that passes through the head center of gravity G and this face surface.

Also, in the present embodiment, the boundary between the crown portion 2 and the sole portion 3 can be defined as follows. That is, in the case where a ridgeline is formed between the crown portion 2 and the sole portion 3, this ridgeline will be the boundary. On the other hand, in the case where a clear ridgeline is not formed therebetween, the contour when the head is set in the reference state and viewed from directly above the center of gravity of the head 10 will be the boundary.

The head 10 can, for example, be formed with a titanium alloy (Ti-6Al-4V, Ti-8Al-1Mo-1V, etc.) having a specific gravity of substantially about 4.3 to 4.5. Apart from a titanium alloy, the head can also be formed using one or two or more materials selected from stainless steel, maraging steel, an aluminum alloy, a magnesium alloy and an amorphous alloy, for example.

The volume of this golf club head 10 is desirably from 90 cm³ to 470 cm³ inclusive, for example.

2. Structure of Inner Surface of Sole Portion

Next, the structure of the inner surface of the sole portion 3 will be described, with reference also to FIGS. 5 to 7. FIG. 5 is a plan view of the sole portion viewed from an internal space side, FIG. 6 is a perspective view showing the internal space of the head, with the head partially cut away, and FIG. 7 is a perspective view from a different angle to FIG. 6.

As shown in FIGS. 5 to 7, the inner surface of the sole portion 3 is provided with a rectangular thin portion (light gray colored portion) 31 and a thick portion 32 (dark gray colored portion) formed so to surround this thin portion 31. Furthermore, a rear area 33 including the fixing hole 38 is formed on the back side of the thick portion.

First, the thin portion 31 will be described. Here, for convenience of description, the face-side outer edge, the toe-side outer edge, the back-side outer edge and the heel-side outer edge of the thin portion 31 will be respectively referred to as a first edge portion 311, a second edge portion 312, a third edge portion 313 and a fourth edge portion 314. The first edge portion 311 is slightly away from the face portion 1, and extends generally parallel to the face portion 1. The second edge portion 312 is in proximity to the toe-side edge portion of the sole portion 3 and extends in an arc along that edge portion. The third edge portion 313 is formed as a straight line that bends part way along, and the heel-side end portion is located further on the heel side than the heel-side end portion of the first edge portion 311. The fourth edge portion 314 is formed so as to extend on the toe side proceeding toward the face side, while extending in the face-back direction. Note that, in the present embodiment, the fourth edge portion 314 is located slightly further on the heel side than the center in the toe-heel direction. That is, the thin portion is formed to span from the center to the toe side in the toe-heel direction. Also, in the face-back direction, this thin portion 31 extends slightly further to the back side than the center in the face-back direction from adjacent to the face portion 1.

The thickness of this thin portion 31 can, for example, be set from 0.3 to 0.6 mm, and is preferably set from 0.35 to 0.45 mm.

Next, the thick portion 32 will be described. The thick portion 32 has a band-like first region 321 that is further on the back side than the third edge portion 313 of the thin portion 31 and a second region 322 that is further on the back side than the fourth edge portion 314, and is arranged so as to surround the back side and heel side of the thin portion 31. The thickness of the thick portion 32 is larger than the thin portion 31, and can, for example, be set from 0.5 to 1.5 mm, and is preferably set from 0.6 to 1.2 mm.

The rear area 33 is arranged on the back side of the first region 321 of the thick portion 32, and is formed so as to follow the back-side edge portion of the sole portion 3. The rear area 33 includes a region formed to be equivalent to or larger than the thick portion 32.

Also, three ribs are formed in the sole portion 3. That is, a large rib 51 extending in the toe-heel direction and a first small rib 52 and a second small rib 53 extending in the face-back direction are formed.

The large rib 51 extends so as to approach the back side proceeding toward the heel side, rather than extending parallel to the face portion 1. The toe-side end portion of the large rib 51 extends to the vicinity of the toe-side edge portion of the sole portion 3, and the heel-side end portion of the large rib 51 extends to the vicinity of the heel-side edge portion of the sole portion 3.

The first small rib 52 extends from the toe side of the sole portion 3 adjacent to the face portion 1, intersects the large rib 51, and extends to the heel side of the sole portion 3 in the vicinity of the back-side end portion. That is, the first small rib 52 extends so as to approach the face side proceeding toward the toe side. On the other hand, the second small rib 53 extends from the heel side of the sole portion 3 adjacent to the face portion 1, intersects the large rib 51 and the first small rib 52, and extends to the toe side of the sole portion 3 in the vicinity of the back-side end portion. That is, the second small rib 53 extends so as to approach the back side proceeding toward the toe side.

In this way, in the present embodiment, the three ribs 51 to 53 extend so as to intersect each other. A triangular area 50 is formed by the three ribs 51 to 53 intersecting. That is, the triangular area 50 is formed by the intersection point of the large rib 51 and the first small rib 52, the intersection point of the large rib 51 and the second small rib 53, and the intersection point of the first small rib 52 and the second small rib 53, and this area 50 is located within the thin portion 31. Also, the back-side end portions of the first small rib 52 and the second small rib 53 are located within the rear area 33.

The height of the large rib 51 from the inner surface of the sole portion 3 can, for example, be set from 3.0 to 7.0 mm, and is preferably set from 4.0 to 6.0 mm. On the other hand, the height of the first small rib 52 and the second small rib 53 is lower than the large rib 51, and can, for example, be set from 0.5 to 4.0 mm, and is preferably set from 1.0 to 3.0 mm. In other words, the height of both of the small ribs 52 and 53 is preferably 10 to 80 percent of the height of the large rib 51.

Also, the height of the large rib 51 becomes lower proceeding toward the toe side and heel side, and the height from the inner surface of the sole portion 3 is zero at both end portions thereof. The small ribs 52 and 53 are the same in this regard, and become lower in height proceeding to both end portions.

The width of the large rib 51 can, for example, be set from 0.5 to 1.0 mm. On the other hand, the width of the first small rib 52 and the second small rib 53 can, for example, also be set from 0.5 to 1.0 mm.

Also, from the viewpoint of the hitting sound discussed later, the large rib 51 is preferably formed near the face portion 1, and is, for example, preferably formed in an area within 50 percent of the length of the head 10 in the face-back direction from the face portion 1.

3. Assembly Structure of Golf Club Head

The golf club head 10 according to the present embodiment can be configured to have various assembly structures. For example, a structure can be adopted in which an opening is formed in the face portion 1, and a face member is fitted into this opening and fixed by welding. The face member can, for example, be manufactured by a method such as forging, plate pressing or casting. On the other hand, portions other than the face member can be manufactured by casting such as a well-known lost wax precision casting process.

Alternatively, a so-called cup face structure can also be adopted in which a cup-shaped face member provided with the face portion 1 and a peripheral portion that projects from a periphery of the face portion 1 are formed, and this cup-shaped face member is attached to an opening formed on the face side of the crown portion 2 and the sole portion 3. In this case, the face member can similarly be manufactured by a method such as forging, plate pressing or casting, as mentioned above, and other portions can be formed by a precision casting process such as the above.

4. Features

According to the above embodiment, the following effects can be obtained.

(1) Since the thin portion 31 is formed in the sole portion 3 and the weight of that portion is reduced, the saved weight can be distributed to other regions. Thus, the flexibility of center of gravity design of the head 10 can be improved. In particular, since the thin portion 31 is formed on the toe side, the weight forward on the toe side can be reduced. On the other hand, since the thick portion 32 having a large thickness is formed rearward on the heel side, the weight rearward on the heel side can be increased. Accordingly, the head readily returns to square during the swing, and slicing can be reduced.

(2) Since the large rib 51 extending in the toe-heel direction is formed so as to pass through the thin portion 31, a decrease in rigidity due to the thin portion 31 can be compensated. In particular, the sole portion 3 is generally longer in the toe-heel direction than the face-back direction, and thus tends to deform in the toe-heel direction. Thus, by forming the large rib 51 to be high in height in the toe-heel direction, this deformation can thus be effectively suppressed. Accordingly, a decrease in rigidity of the sole portion 3 can be suppressed, and, as discussed later, lowering of the pitch of the hitting sound can be prevented. Note that given that deformation is smaller than the curved surface that runs in the toe-heel direction, the height of the small ribs 52 and 53 is lower than the large rib 51.

Furthermore, since a configuration is adopted in which the triangular area 50 formed by the three ribs 51 to 53 intersecting and having a particularly high rigidity is located in the thin portion 31, the decrease in rigidity due to the thin portion 31 can be effectively compensated.

Also, the head vibrates due to the ball hitting the face portion 1. At this time, antinodes of vibration of comparatively low order and low vibration frequency may occur in the toe-heel direction of the sole portion 3. When the large rib 51 extending in the toe-heel direction is formed so as to pass through the portion where such antinodes of vibration occur, the large rib 51 contribute to restraining the vibration, and the first-order natural vibration frequency can be increased. In particular, the antinodes of vibration of comparatively low order and low vibration frequency often occur adjacent to the face portion 1 so as to be aligned in the toe-heel direction, and thus by forming the large rib 51, as in the present embodiment, such vibration of comparatively low order and low vibration frequency can be restrained, and the pitch of the hitting sound can be increased.

In this regard, simulation related to vibration of the sole portion was performed for a head of the same shape as the golf club head according to the present embodiment. First, three-dimensional data of a head having a similar shape to this head was created. The shape of the sole portion 3 of this head is generally as shown in FIG. 8. The thickness of the thin portion 31 of the sole portion 3 was 0.45 mm, and the thickness of the thick portion 32 was 0.6 mm. Also, the head volume was 460 cc. Titanium alloy was selected as the material of the head, and calculations were performed using coefficients that were based on this material. The head weight was 190 g.

Next, mesh division of a head 10 was performed on a finite element, using a commercial preprocessor (HyperMesh, etc.), and a calculation model was obtained. Next, eigenvalue analysis was performed using commercial eigenvalue analysis software, and the natural vibration frequency and mode shape were calculated. The simulation was also performed for a head that was not provided with a large rib. The results areas shown in FIGS. 9A and 9B. Note that although the heads of FIGS. 9A and 9B differ partially from FIG. 8 in the shaping of the sole portion, this simulation was performed using the shape of FIG. 8 as mentioned above.

FIG. 9A shows the amplitude distribution of the first-order natural vibration frequency of the sole portion 3 when a ball is hit with the head of the present embodiment. On the other hand, FIG. 9B shows the amplitude distribution of the first-order natural vibration frequency of the sole portion 3 when a ball is hit with the head that is not provided with the large rib. In these FIGS. 9A and 9B, the dark portions are where the amplitude is largest. In the simulation shown in FIG. 9A, a vibration mode in which the first-order natural vibration frequency is 3995 Hz is shown. On the other hand, in the simulation shown in FIG. 9B, a vibration mode in which the first-order natural vibration frequency is 3401 Hz is shown.

Comparing these heads, in FIG. 9B, two antinodes of vibration that are aligned in the toe-heel direction occur in the sole portion, but by providing the large rib 51 so as to pass through the portion where the antinodes of vibration occur, the first-order normal vibration changes to 3995 Hz, as shown in FIG. 9A. That is, it is evident that by providing the large rib 51, the first-order natural vibration frequency increases and the hitting sound increases in pitch.

Since the large rib 51 according to the present embodiment suppresses vibration of comparatively low order and low vibration frequency and maximizes the first-order natural vibration frequency in this way, a sound that is pleasing to the golfer can be produced when the ball is hit.

(3) By providing the two small ribs 52 and 53 extending in the toe-heel direction, the rigidity in the face-back direction can be improved. Accordingly, deformation in the face-back direction can be suppressed and the rebound performance can be improved. In particular, since the small ribs 52 and 53 are formed to intersect so as to extend in opposite directions to each other and, to also further intersect the large rib 51, the rigidity of the intersecting portion can be enhanced, and the rebound performance can be further improved.

In this way, in the present embodiment, the large rib 51 that is high in height is provided in the direction in which deformation is large, and the low small ribs 52 and 53 are formed in the direction in which deformation is smaller. Since these ribs are made to intersect, the rigidity of the sole portion 3 can be further enhanced, and the rebound performance can be improved as a result.

(4) Since both end portions of each of the ribs 51 to 53 extend to the vicinity of the edge portion of the sole portion 3 where there is little deformation, the effect of reinforcement by the ribs 51 to 53 can be enhanced.

(5) Since the rear area 33 having a large thickness is formed on the back side, the center of gravity depth of the head 10 can be increased. Thus, the sweet spot can be raised, and the launch angle of the ball can be improved.

5. Variations

Although an embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention. Also, the following variations can be combined as appropriate. For example, the following modifications can be made.

5-1. The thin portion 31 is not particularly limited in terms of shape, position and number, and can, for example, also be formed on the heel side or the back side. Also, a configuration may be adopted in which the thin portion 31 is not provided.

5-2. The large rib 51 need only extend in the toe-heel direction, and the position and shape thereof are not particularly limited. In the above embodiment, the large rib 51 is formed to be lower at both end portions, but the height of the large rib 51 is not particularly limited, and the low portion can be changed as appropriate according to the performance that is required. Also, the height of the large rib 51 may change incrementally, or a configuration can also be adopted in which the height is changed by providing a step. Alternatively, a configuration can also be adopted in which the height of the large rib 51 is uniform.

5-3. The small ribs 52 and 53 need only extend in the face-back direction, intersect the large rib 51, and be lower in height than the large rib 51, and the position and shape thereof are not particularly limited. The height of the small ribs 52 and 53 can be changed as appropriate similarly to the height of the abovementioned large rib 51. For example, the heights of the plurality of small ribs may be the same or may differ. Also, the intersection position of the small ribs 52 and 53 is not particularly limited. Also, the small ribs 52 and 53 need not intersect.

5-4. Any of the large rib 51 and the small ribs 52 and 53 need only be formed so as to pass through the thin portion 31, and all of the ribs 51 to 53 need not pass through the thin portion 31. Also, the large rib 51 and the small ribs 52 and 53 are not particularly limited in number, and may be other than the above embodiment. For example, a configuration having two or more large ribs and one small rib can also be adopted. Alternatively, a configuration may be adopted in which all the ribs 51 to 53 do not pass through the thin portion 31. A configuration can also be adopted in which only the ribs 51 to 53 are formed, without providing the thin portion 31 in the sole portion 3. The effects of the abovementioned ribs can also be obtained by adopting these configurations.

5-5. In the above embodiment, the large rib 51 and the small ribs 52 and 53 extend to the vicinity of the edge portion of the sole portion 3, but both end portions need not reach the edge. The ribs 51 to 53 can also be formed such that one of the two end portions thereof reaches the edge portion of the sole portion 3.

5-6. The positional relationship between the large and small ribs can be variously configured, examples of which are shown in FIGS. 10A to 10E. In the example of FIG. 10A, the intersection position of the two small ribs 52 and 53 is further on the face side than the large rib 51.

In the example of FIG. 10B, the two small ribs 52 and 53 extend generally parallel in the face-back direction, without intersecting. In the example of FIG. 10C, the two small ribs 52 and 53 intersects further on the back side than the large rib 51, and the face-side end portion of the small ribs 52 and 53 contacts the large rib 51. In the example of FIG. 10D, the two small ribs 52 and 53 contact the large rib 51, but the small ribs 52 and 53 are only arranged further on the face side than the large rib 51 and do not intersect. In this way, the small ribs 52 and 53 may merely contact rather than intersect the large rib 51. In order to improve the rigidity of the sole portion 3, however, the small ribs 52 and 53 preferably intersect the large rib 51. In the example of FIG. 10E, only one small rib 52 is provided. As mentioned above, the position at which the small ribs 52 and 53 are arranged is not particularly limited, and the small ribs 52 and 53 need not necessarily intersect, and, furthermore, in the case where the small ribs 52 and 53 intersect each other, the position of the intersection is also not particularly limited.

5-7. The thickness of the sole portion 3 is not limited to that shown in the above embodiment, and various thickness distributions can be configured. For example, the thick portion 32 need only be formed at least partially around the thin portion 31, and the shape thereof is not particularly limited. The shape of the rear area 33 is also not particularly limited, and a configuration can also be adopted in which such a rear area 33 is not provided.

LIST OF REFERENCE NUMERALS

-   -   1 Face portion     -   2 Crown portion     -   3 Sole portion     -   31 Thin portion     -   32 Thick portion     -   51 Large rib (first rib)     -   52 First small rib (second rib)     -   53 Second small rib (second rib) 

What is claimed is:
 1. A golf club head comprising: a face portion; a crown portion; a sole portion; at least one first rib provided in the sole portion; and at least one second rib provided in the sole portion, wherein the golf club head has an internal space surrounded by the face portion, the crown portion and the sole portion, the first rib extends in a toe-heel direction on an inner wall surface of the sole portion, the second rib extends in a face-back direction on the inner wall surface of the sole portion, and a height of the second rib from the inner wall surface of the sole portion is lower than a height of the first rib from the inner wall surface of the sole portion.
 2. The golf club head according to claim 1, wherein the second rib intersects the first rib.
 3. The golf club head according to claim 1, wherein the first rib and the second rib each extend continuously.
 4. The golf club head according to claim 1, wherein a thin portion having a thinnest thickness is provided in the sole portion, and the first rib and the second rib are constituted to at least partially pass through the thin portion.
 5. The golf club head according to claim 4, wherein the thin portion is arranged on a toe side in the toe-heel direction.
 6. The golf club head according to claim 4, wherein a thick portion having a larger thickness than the thin portion is provided in the sole portion at least partially around the thin portion, and at least one of the first rib and the second rib extends to the thick portion.
 7. The golf club head according to claim 1, comprising: at least two of the second rib, wherein the two second ribs are formed so as to intersect in the sole portion.
 8. The golf club head according to claim 7, comprising: one of the first rib, wherein an area surrounded by the one first rib and the two second ribs is arranged in the thin portion.
 9. The golf club head according to claim 1, wherein the second rib extends on a back side from a vicinity of a boundary between the face portion and the sole portion. 